1. Field of the Invention
The present invention relates generally to electromagnetic interference (EMI) shields for transceiver and transponder modules.
2. Description of the Related Art
It is desirable to provide electromagnetic interference (EMI) shielding in transceiver and transponder modules. One portion of a transceiver/transponder module for which EMI shielding is desirable is in a fiber connector end of the module. High-speed electronics, such as transmitter or receiver circuits operating at data rates greater than 1 Gb/s, may generate significant EMI if not properly shielded. Consequently, in many applications EMI shielding is required.
One application requiring EMI shielding of port housings is a small form factor transceiver, including both hot-pluggable and non-pluggable (i.e., hard soldered) varieties. An industry-wide Multi-Source Agreement (MSA) governs the size and pin arrangement of small form factor transceivers. Conventionally, the port housings of a transceiver/transponder module are fabricated from metal. However, there is increasing interest in plastic port housings. Plastic port housings provide several potential advantages, such as the ability to integrate a plastic lens into the housing. However, compared with metal port housings, plastic port housings have lower mechanical strength. Moreover, plastic port housings may suffer more from thermal stress. Additionally, plastic port housing are more difficult to shield from EMI.
Therefore what is desired is an EMI shield compatible with the requirements of plastic port housings and which has desirable EMI shielding and mechanical properties.
An optical transceiver/transponder module includes optical sub-assemblies having port housing fabricated from an optical plastic or other insulating material. The neck portion of each port housing is supported within an electrically conductive yoke. An electrically conductive cap on the port housing provides additional EMI shielding of the optical sub-assemblies in addition to that provided by the yoke. In one embodiment, each optical sub-assembly comprises: an optical port housing formed of a non-conductive material and having a body portion having an open receptacle end and an optical coupling end, a ferrule portion having a bore shaped to receive an optical fiber; a neck portion connecting the optical coupling end of the body portion to the bore of the ferrule portion; an active optical device disposed in the receptacle end of the body portion of the optical port housing; and an electrically conductive cap disposed on an outer surface of the port housing to reduce electromagnetic interference.